塔里木盆地轮南低凸起奥陶系原油运移示踪研究

Research on the trace of Ordovician crude oil migration in Lunnan uplift,Tarim Basin

原油在二次运移过程中,其成分往往沿充注路径发生梯度性变化。储层中原油成熟度的最高点对应油气的充注点,油气自成熟度高的部位向成熟度低的部位运聚。通过对轮南低凸起奥陶系原油饱和烃成熟度指标Ts/(Ts+Tm)、Tric/(Tric+17αβ-H)的系统分析,认为该区存在2个油气充注方向。奥陶系油气藏中原油Ts/(Ts+Tm)、Tric/(Tric+17αβ-H)的极值点位于东南部的LG35及LG353井区,且绝大部分样品的成熟度自东南向西北出现依次递减的趋势,表明轮南地区奥陶系原油的主力充注方向来自于东南。在研究中,将油气主充注期(海西晚期)奥陶系潜山顶面的古地貌形态与运移示踪指标的平面分布特征相结合,认为桑塔木断垒带控制了油气自烃源灶向轮南潜山低势区的运聚,主干路径为LG353—LN631—LN48—LG11—LN39—LN44C—LG4—LG7(LN1);另一方面,LG7及LN1井区运移示踪的结果表明其油气主要来自于西南部的塔河油田,油气充注路径为LN11—LN11(H1)—LG701。

There is a stepped alternation in crude oil composition along the migration path during the secondary migration of crude oil.The highest point of crude oil maturity corresponds to the charging point of hydrocarbon in reservoir,and the hydrocarbon migrates from high maturity area to low one.Through analyzing the saturated hydrocarbon maturity index Ts/（Ts＋Tm） and Tric/（Tric＋17α β-H） for Ordovician crude oil in Lunnan low uplift,it is believed that there are two hydrocarbon charging directions in this area.The area with the extreme point of Ts/（Ts＋Tm） and Tric/（Tric＋17αβ-H） is located in the southeastern LG35 and LG353 well fields of Lunnan uplift.The maturity of most oil samples decreases successively from southeast to northwest,which shows that the main charging direction of Ordovician crude oil in Lunnan Area comes from the southeast.From rebuilding the the morphostructure of surface of burial hill,it is believed that Sangtamu faulting belt controls the hydrocarbon accumulation from source rocks to low fluid potential area of Lunnan buried hill during the study,combined the palaeogeomorphology conformation of Ordovician buried hill surface at the main hydrocarbon charging stage（late Hercynian period） with the plane distribution characteristics of migration tracing index.Main paths are LG353-LN631-LN48-LG11-LN39-LN44C-LG4-LG7（LN1）.Alternately,the migration tracing result in LG7 and LN1 well fields shows that the hydrocarbon mainly comes from the southwestern Tahe Oilfeild and its charging path is LN11-LN11（H1）-LG701.